1. Field of Invention
The invention relates to the reduction of aerodynamic drag for moving ground vehicles; specifically to an improved method and device for the reduction of aerodynamic drag, the improvement in operational performance and an increase in fuel economy of multiple component vehicles by lowering the pressure acting on the front face of the trailing vehicle or vehicle component by controlling the air flow in the gap between the leading vehicle component and the trailing vehicle component.
2. Description of Prior Art
It is known by those skilled in the art that the aerodynamic drag for a multiple component vehicle such as a tractor-trailer truck increases with increasing separation distance between the tractor and the trailer. The separation distance between the aft facing rear surface of a tractor and/or tractor mounted aerodynamic fairings and the forward facing front surface of the trailer is referred to as the gap distance. It is also known by those skilled in the art that the amount of air that enters the gap and thus the aerodynamic drag increases with increasing crosswind flow. In the prior art there have been attempts to reduce the aerodynamic drag resulting from flow in the gap region. Prior art show the use of both aerodynamic fairings mounted on the tractor cab roof and extensions attached to the side of the tractor cab to close the gap distance between the tractor and the trailer. A reduction in the gap distance will reduce or eliminate gap flow and thereby reduce aerodynamic drag, see U.S. Pat. Nos. 5,536,062, 4,142,755, 3,945,677, and 3,834,572. These gap closure devices, while successful in reducing or eliminating gap flow, are typically complex devices that are comprised of moving parts that require maintenance and add weight to the vehicle. The increased weight and complexity of the devices has a negative impact on operational performance of the vehicle and interfere with other vehicle systems.
Other concepts as documented in U.S. Pat. Nos. 5,280,990, 3,971,586, 3,697,120, 3,934,922 and 3,866,967 re-contour or modify the forward facing front surface of the trailer to reduce the aerodynamic drag of the trailer. The drag reduction results from the gap flow impinging on a trailer front surface with a curved surface instead of the typical flat surface. These trailer front surface mounted devices reduce the aerodynamic drag for the no crosswind condition, but the devices do not provide significant drag reduction when crosswind flow is present. The subject devices consist of complex shapes provide aerodynamic drag reduction over a limited range of vehicle operational conditions and these devices do not provide significant aerodynamic drag reduction at crosswind flow conditions. The majority of these types of devices are comprised of moving parts that add complexity and require maintenance. All of these devices would add significant weight to the vehicle. These above listed attributes of these devices have a negative impact on vehicle operational performance and interfere with normal operations of the vehicle.
U.S. Pat. Nos. 4,257,640, 4,068,883 and 4,035,013 apply a vertical surface located on the vehicle centerline that connects the tractor base to the trailer front surface to reduce the aerodynamic drag resulting from gap flow. These devices are complex and comprised of moving parts that require maintenance. These devices interfere with normal operations of the truck and add weight to the vehicle that would has a negative impact on operational performance of the vehicle.
Several concepts have attempted to minimize the negative effect of crosswind conditions on aerodynamic drag and stability of tractor-trailer truck systems. U.S. Pat. No. 5,526,062 adds a plurality of fairings and vents to the tractor in an effort to control the flow impinging on the tractor and then passing into the gap region between the tractor and trailer. U.S. Pat. No. 3,348,873 adds a plurality of fairings to the tractor in an effort to control the flow impinging on the tractor and passing into the gap region between the tractor and trailer. These two patents provide drag reduction but are complex devices that are comprised of moving parts. These devices also interfere with normal operations of the truck and add weight to the vehicle. These characteristics of the devices result in a negative impact on the vehicle operational performance.
U.S. Pat. No. 4,867,397 adds a pair of thin rigid vertical plates to the forward surface of a vehicle body to control the separation and reattachment of the flow at the corners of a flat-faced body and thereby reduce drag. This patent would only be useful for vehicles that have not been designed in accordance with existing best practices that radius the corners of such bodies and vehicles to accomplish the drag reduction goal. The patent does not take advantage of crosswind conditions. The patent does not provide drag reduction for a forward facing surface located in the gap of a multiple component vehicle.